NTNU Norwegian University of Science and Technology Faculty of Engineering Department of Marine Technology
Thea Kruse ValvatneAssembly Port for Floating Offshore Wind Turbine
Thea Kruse Valvatne
Assembly Port for Floating Offshore Wind Turbine
Early phase design planning
Master’s thesis in Marine Systems Design Supervisor: Stein Ove Erikstad
Co-supervisor: Marco Semini June 2021
Master ’s thesis
Thea Kruse Valvatne
Assembly Port for Floating Offshore Wind Turbine
Early phase design planning
Master’s thesis in Marine Systems Design Supervisor: Stein Ove Erikstad
Co-supervisor: Marco Semini June 2021
Norwegian University of Science and Technology Faculty of Engineering
Department of Marine Technology
Master thesis in Marine Systems Design Thea Kruse Valvatne
Port logistics for constructing floating offshore wind turbines Spring 2021
Background
Floating offshore wind is standing at the edge of being commercialized. As economics of scale dictates, the more units are being produced, the costs of each unit will be reduced. For this upscaling in production to happen, an effective production line in port is needed.
Overall aim
The project’s overall aim is showing, by using a systematic approach, how a port layout for the assembly of floating wind turbines can be developed in an early stage.
Scope and main activities
The candidate should presumably cover the following main points:
1. Provide a short overview of the current status and important development trends related to floating offshore wind.
2. Present logistic solutions for arrival of incoming parts, activities, equipment and storage require- ments
3. Systematize relations and sizes between different activities and areas 4. Use a systematic approach for time scheduling of project planning
5. Present suggestions on design layouts, and based on evaluation criteria choose the ”best” design 6. Discuss and conclude
Modus operandi
At NTNU, Professor Stein Ove will be the responsible advisor.
The work shall follow the guidelines given by NTNU for the MSc Project work
Sammendrag
Markedet for flytende vindturbiner øker, og det er forventet sterk vekst de kommende ˚arene, og vindkraft vil bli en av de viktigste kildene til fornybar energi. I dag er flytende havvind lite utbredt, men Norge er en av f˚a nasjoner som allerede har f˚att til pilotprosjekt, som for eksempel Hywind Tampen utenfor Skottland. Fordelen med flytende vindturbiner er at omr˚adene disse kan st˚a p˚a er mye mer fleksibelt enn fastmonterte, som per i dag ikke kan plasseres p˚a vanndybder større enn 60 meter.
Det er flere metoder ˚a bygge en flytende vindturbin, det kan deles inn i to hovedm˚ater: vindturbinen bygges til havs, eller at vindturbinene ferdigstilles i havn og slepes ut til vindmølleparken. M˚alet med denne oppgaven er ˚a utforme ved hjelp av metode fra ”Systematic Layout Planning MUTHER, R. &
LEE, H. L.” et design p˚a en havn for ˚a sette sammen en flytende vindturbin, før den blir slept ut til en vindturbinpark. Forh˚apentligvis kan dette bidra til utviklingen i møte med det grønne skiftet.
Oppgaven har satt visse rammebetingelser: En vindturbin som skal settes sammen best˚ar av to t˚arndeler, tre vindturbinblad, en nacelle og en hub. Den flytende substrukturen er en semi-submersible plattform. Størrelsesordenen p˚a vindturbinen er satt til 6-8 MW. Designfasen er begrenset til Fase II, som innebærer at resutlatet vil være et overordnet design av en havn, og at plasseringen av havnen ikke er lokalisert.
I denne oppgaven er metoden for ˚a sette sammen vindturbinen som følgende: t˚arnkomponenter settes sammen og monteres til den flytende substrukuren, nacellen monteres p˚a t˚arnet, hub og blader settes sammen p˚a bakken før hele rotoren løftes og monteres p˚a nacellen. Deretter blir den ferdige turbinen slept til vindturbinparken.
Planleggingen av ˚a designe en havn starter med ˚a identifisere alle aktivitene som m˚a gjøres. For eksempel: transportere blader fra havn til lagringsomr˚ade, eller sette sammen nacelle og blader og en beskrivelse av hvordan disse aktivitetene utføres. Flyten av de ulike aktivitetene og deres relasjoner vil bli illustrert i et flyt-diagram. Deretter blir hver aktivitet knyttet til et omr˚ade, og et relasjonskart blir utviklet ved ˚a analysere viktigheten av nærhet mellom de ulike omr˚adene. Dette kan være avhengig av
˚a ha minst mulig transport, deling av utstyr for ˚a minimere tid osv.
For ˚a lage et tidsestimat og f˚a oversikt over hva som er kritisk i planleggingen er nettverkdiagram blitt brukt. Da er det estimert for alle aktivtetene hvor lang tid de tar, og s˚a hvilken avhengighet de har med tanke p˚a hva som m˚a være ferdig før neste aktivtet kan begynne. For eksempel kan ikke sam- mensetting av hub og blader begynne før disse kompoentene er brakt til sammenstillingsomr˚adet. Ut ifra dette diagrammet, ”Activity on node”, kan man lese hvor mye flyt hver aktivtet har (hvor sent en aktivitet kan begynne) uten ˚a p˚avirke sluttiden for sammenstillingen av en hel turbin. ”Kritisk vei” blir ogs˚a identifisert i dette diagrammet.
Til alle aktiveteter er et overordnet estimat av ressursbehov kartlagt, og knyttet opp til hva slags utstyr som trengs for ˚a sette sammen b˚ade ´en, og fem turbiner. Utifra disse estimatene, tillegg til kom- ponetstørrelsene til turbinen, er størrelsen til hvert av de ulike omr˚adene kalkulert. Ved ˚a kombinere størreslen til de ulike omr˚adene og relasjonsdiagrammet kan et ferdig design av en havnelayout designes.
Noen forskjellige forslag er blitt laget og evaluert. Evalueringen er basert p˚a ressursbruk for hver aktivitet, avstand mellom de ulike omr˚adene, intensiteten til flyten mellom ulike omr˚adene og plassutnyttelse. Avs- luttende en evaluering om designet er praktisk og om det realistisk kan la seg gjennomføre.
Summary
The market for floating wind turbines is growing, and strong growth is expected in the coming years, and wind power will be one of the most important sources of renewable energy. Today, floating offshore wind is not widespread, but Norway is one of the few nations with pilot projects, such as Hywind Tampen outside Scotland. The advantage of floating wind turbines is that the areas they can stand on are much more flexible than fixed ones, which as of today cannot be placed at water depths greater than 60 meters.
Several methods of building a floating wind turbine can be divided into two main ways: the wind turbine is built at sea, or that the wind turbines are completed in port and towed out to the wind farm.
This thesis aims to design a port, using the method from ”Systematic Layout Planning MUTHER, R. &
LEE, H. L.” a port design for assembling a floating wind turbine before it is towed out to a wind farm.
Hopefully, this can contribute to the development in the face of the green shift.
The thesis has set certain framework conditions: A wind turbine to be assembled consists of two tower parts, three wind turbine blades, a nacelle and a hub. The floating substructure is a semi-submersible platform. The order of magnitude of the wind turbine is set at 6-8 MW. The design phase is limited to Phase II, resulting in an overall port design.
In this exercise, the method of assembling the wind turbine is as follows: tower components are assem- bled and mounted to the floating substructure, the nacelle is mounted on the tower, hubs and blades are assembled on the ground before the entire rotor is lifted and mounted on the nacelle. Then the finished turbine is towed to the wind farm.
Designing a port starts with identifying all the activities that need to be done—for example, trans- porting turbine blades from port to storage area, assembling nacelle and blades, and describing how these activities are performed. The flow of the various activities and their relationships will be illustrated in a flow diagram. Then, each activity is linked to an area, and a relationship map is developed by analyzing the importance of proximity between the different areas. This may depend on having the least possible transport, sharing equipment to minimize time, etc.
Time estimates and creating an overview of critical parts in the planning, Network diagram have been used. Time estimates for all the activities and dependency of wheat activities must be finished before the next activity is set. For example, assembly of hubs and blades cannot begin until these components have been brought to the assembly area. Based on this diagram, ”Activity on node”, one can read how much flow each activity has (how late an activity can begin) without affecting the end time for the assembly of an entire turbine. ”Critical path” is also identified in this diagram.
An overall estimate of resource and equipment needs has been mapped for each activity. Based on
these estimates and the component sizes, the size for each area is calculated. By combining the size of the different areas and the relationship diagram, a finished configuration of a port layout design can be created. Some different proposals have been made and evaluated. Evaluation is based on resources for each activity, distance between different areas, and the intensity of the flow between the different areas.
Finally, an evaluation of whether the design is practical and whether it can realistically be implemented.
Preface
This master thesis is a part of the specialization course TMR4560 - Marine Systems Design at the Nor- wegian University of Science and Technology. The work load counts for 30 credits.
The overall goal of the assignment is to look at different design configurations of as assembly port for floating offshore wind turbines. This involves identifying all activities that are needed to assembly a wind turbine, address spaces and it sizes needed, and put them together in different configurations.
I want to thank my supervisor, Professor Stein Ove Erikstad at the Department of Marine Technol- ogy, NTNU for guidance and helpful discussion about my thesis, and a huge thanks to co-supervisor, Associate Professor Marco Semini at the Department of Mechanical and Industrial Engineering, NTNU, for taking the time to guide me as well.
In addition I want to thank my family for support, and valuable discussions about my thesis at the end of the semester.
21th june, 2021
Thea Kruse Valvatne
Contents
1 Introduction 1
1.1 Background and motivation . . . 1
1.2 Objectives . . . 1
1.3 Content of thesis . . . 2
2 Litterature study 3 2.1 The turbine . . . 3
2.1.1 Typical dimensions for a 6-8 MW floating wind turbine . . . 3
2.1.2 Floating substructure . . . 4
2.1.3 Tower . . . 7
2.1.4 Blades . . . 7
2.1.5 Nacelle . . . 7
2.1.6 Anchor system . . . 7
2.2 Supply chain . . . 8
2.2.1 Integrated supply chain . . . 9
2.2.2 Example of supply chain management for floating wind projects set in production: Hywind Scotland . . . 10
2.3 Assembly methods . . . 11
3 Theory 13 3.1 Phases of layout planning . . . 13
3.2 Activities and relations . . . 15
3.2.1 List activities . . . 15
3.2.2 Deciding flow of materials . . . 15
3.2.3 Relationship chart . . . 16
3.2.4 Relationship diagram . . . 16
3.3 Project planning . . . 17
3.3.1 Network diagram . . . 17
3.3.2 Network analysis . . . 17
3.3.3 Resource charts . . . 18
3.4 Space determinations . . . 20
3.4.1 Address spaces . . . 20
3.4.2 Equipment needed . . . 20
3.4.3 Space requirements . . . 20
3.5 Making suggestions on layout designs . . . 22
3.5.3 Evaluation of layout design . . . 24
4 Methodology 25 4.1 Activities when assembling a floating wind turbine . . . 25
4.1.1 Activity 1: Ship docking of components . . . 27
4.1.2 Activity 2: Transportation of arriving components (tower, blades, nacelle, hub) from ship to quayside . . . 27
4.1.3 Activity 3: Arrival of the floating sub structure . . . 29
4.1.4 Activity 4: Transporting components from quayside to storage area . . . 29
4.1.5 Activity 5: Securing floating sub structure to quay side . . . 30
4.1.6 Activity 6: Storing of components . . . 30
4.1.7 Activity 7: Transportation of tower from storage area to assembly area . . . 31
4.1.8 Activity 8: Transport blades from storage area to assembly area . . . 31
4.1.9 Activity 9: Transport hub from storage area to assembly area . . . 31
4.1.10 Activity 10: Assembling of tower components . . . 31
4.1.11 Activity 11: Assembling hub and blades . . . 32
4.1.12 Activity 12: Preparing floating sub structure for turbine components . . . 33
4.1.13 Activity 13: Transportation of assembled tower to quayside . . . 33
4.1.14 Activity 14: Transportation of nacelle to quayside . . . 33
4.1.15 Activity 15: Transportation of assembled hub and blades to quayside . . . 33
4.1.16 Activity 16: Mounting of tower onto floating sub structure . . . 33
4.1.17 Activity 17: Mounting of nacelle onto tower on sub structure . . . 34
4.1.18 Activity 18: Hub and blades lifted and mounted onto nacelle on floating sub structure 34 4.2 Activity relationships . . . 36
4.2.1 Material flow . . . 36
4.2.2 Relationship chart . . . 38
4.2.3 Relationship diagram . . . 39
4.2.4 Service areas . . . 40
4.3 Project planning . . . 41
4.3.1 Network diagram/analysis . . . 41
4.3.2 Resource chart . . . 44
4.4 Equipment needed in the execution phase . . . 46
4.4.1 Self Propelled Modular Trailer (SPMT) . . . 46
4.4.2 Crane . . . 47
4.5 Space size determinations . . . 49
4.5.1 Space requirements . . . 49
4.5.2 Main aisles . . . 54
4.5.3 Up scaling (to five turbines) . . . 54
4.5.4 Total space needed . . . 54
4.5.5 Space Relationship Diagram . . . 56
4.6 Evaluation of design layouts . . . 58
4.6.1 Combination of distance, flow intensity and resource need . . . 58
4.6.2 Space utilization . . . 60
4.6.3 Risks and opportunities . . . 60
4.6.4 Possibility for expansion of design . . . 60
4.7 Design layouts . . . 61
4.7.1 Design based on flow diagram . . . 61
4.7.2 Design based on relationship diagram . . . 63
4.7.3 Design based on combination of Direct and Central system . . . 64
4.7.4 Design with oblong storage areas . . . 66
4.7.5 Design with advantages from the direct-and-central-layout, relocated main aisles . 68 5 Evaluation and conclusion 71 5.1 Evaluation . . . 71
5.2 Conclusion . . . 74
6 Discussion 76 6.0.1 Early choices . . . 76
6.0.2 Systematic Layout Planning . . . 77
6.0.3 Project planning . . . 78
6.0.4 Space determinations . . . 79
6.0.5 Developing design layouts . . . 80
6.0.6 Evaluation criteria . . . 80
6.0.7 Conclusion . . . 81
Appendix 87
A Resource requirements per activity 87
B Area relationship reasons 88
C Resource requirements per hour 90
D Activity On Node network 92
E Space relationship diagram based on relationship diagram 93
H Python results, first attempt 97
I Scaled areas in port 99
List of Figures
1 Substructures [40] . . . 5
2 supply chain floating wind turbine . . . 8
3 Simplified sketch of main actors in production of a floating wind turbine . . . 9
4 Supply Hwind Scotland . . . 10
5 Turbine parts . . . 11
6 Activities in flow of materials . . . 15
7 Activity areas in relationship diagram . . . 16
8 Systems describing how movements can be tied together [32] . . . 24
9 Tower to port [39] . . . 27
10 Nacelle on SPMT[12] . . . 28
11 SPMT lifting nacelle/hub . . . 28
12 Blades arriving in port [46] . . . 28
13 Storage of floating sub structure[4] . . . 29
14 Transportation blades [44] . . . 31
15 Pipe turning roll [37] . . . 32
16 Storage of floating sub structure[4] . . . 34
17 Flow chart . . . 37
18 Relationship chart . . . 39
19 Relationship diagram . . . 40
20 Activity On Node network . . . 42
21 AON table . . . 43
22 Number of resources per hour . . . 45
23 Sweeping area tower . . . 49
24 Design layout based on flow diagram . . . 61
25 Port layout based on relationship diagram . . . 63
26 Port design based on Direct and Central flow of components . . . 65
27 Design with oblong storage areas . . . 67
28 Port design with advantages from direct and central and relocated main aisles . . . 69
29 Final layout design: design based on relationship diagram . . . 74
30 Suggestion on final design . . . 75
List of Tables
1 Typical dimensions for a 6-8 MW floating wind turbine [10][23] . . . 3
2 Typical dimensions for a floating wind turbine foundation [45][10][23] . . . 4
3 Stability for substructures [36] . . . 4
4 Floating substructures [15] [36][3] . . . 6
5 Assembling a turbine [39] . . . 12
6 Phases of Systematic Layout Planning [32] . . . 13
7 Variables for activities . . . 18
8 Variables in an AON network . . . 18
9 5 ways of determining space requirements . . . 21
10 Variables . . . 41
11 Variables for assemble hub and blades . . . 41
12 Critical path . . . 44
13 Self propelled modular trailer [16] [26] . . . 46
14 SPMT activities . . . 47
15 Crane data [7] [42][24][22][33] . . . 47
16 Required crane activities . . . 48
17 Space required for components . . . 50
18 Quayside, Ro-Ro/Lo-Lo . . . 51
19 Storage area for tower, blade, nacelle, hub . . . 52
20 Assembling tower components space requirements . . . 52
21 Assembling hub and blades space requirements . . . 53
22 Quayside floating sub structure requirements . . . 53
23 Area spaces for one turbine . . . 55
24 Area needed for 5 wind turbine-construction . . . 56
25 Scaling the layout . . . 57
26 Resource requirements for transportation . . . 60
27 Data port based on flow diagram . . . 62
28 Utilization for design based on flow diagram . . . 62
29 Data port based on relationship diagram . . . 64
30 Utilization for design based on relationship diagram . . . 64
31 Data port based on Direct and central travel routes . . . 66
32 Utilization for design based on combination of Direct and Central system . . . 66
33 Data port with oblong storage areas . . . 68
34 Utilization for design based on oblong storage areas . . . 68
35 Data port with advantages from the direct-and-central-layout, relocated main aisles . . . 70
36 Space utilization for design based on advantages from the Direct-and-Central-layout, with
relocated main aisles . . . 70
37 Evaluation of designs . . . 73
38 Rating the importance of closeness between activity areas . . . 88
39 Reasons for closeness . . . 88
1 Introduction
1.1 Background and motivation
Over the years to come, increased energy demand is expected in order to maintain and develop the stan- dard of living for the world’s population. For a long period of time, the oil and gas industry has been the main energy provider within the transportation sector. However, the demand for renewable, green energy is increasing . Offshore wind power will become increasingly important to meet this demand, and the production of wind turbines needs to be up-scaled in order to meet the needs.
Due to its natural conditions, Norway will be in a position to take a share in the production of re- newable energy. Norway has long traditions from the maritime industry, well positioned to participate in developing facilities producing energy offshore, including offshore wind turbines. The market is, however still immature, affecting the access to investment capital. The energy sector is still under change, and investors’ interest in renewable energy is expected to increase as non-renewable energy is gradually phased out. As an example, the Norwegian Government Pension Fund has withdrawn from investments in coal and oil, whilst interest in the renewable project is high on the agenda[18].
Like oil production, offshore wind energy may be produced from either floating or bottom fixed in- stallations. Bottom-fixed installations have been on the market for a period, i.e. in Denmark. Due to our depth conditions, floating installations will be more applicable to Norway. The technology and cost development for floating offshore wind turbines is still more uncertain than for the bottom-fixed market.
However, several countries, there under Norway, Portugal, Spain, the UK and France, have reported that they will join the pre-commercial floating offshore wind projects over the coming 3-4 years [25]. The early starters may lay the ground for designing and producing wind energy constructions, both on- and offshore.
Today’s production of floating wind turbines is still in a pilot phase, and no standardized method for constructing them has been developed.
1.2 Objectives
By increasing the level of standardization in the production of wind turbines and its supporting infras- tructure, the basis for up scaling of the production may evolve. The ultimate objective should be to enable the industry to benefit from economic of scale. On this background, the main objective for the thesis is to make a small contribution to the evolvement. The objective of the thesis is to summarize and systemize relevant existing knowledge and methods applicable in developing an assembly port for floating wind turbine. Furthermore, the methods are being applied in a specific case study.
Through a systematic approach, an early phase General Overall Layout of an assembly port for floating
wind turbines, with pre-determined properties, will be developed and discussed.
In the thesis, the main theories are taken for ”Systematic Layout Planning” by Richard Muther and Lee Hales[32] will be used, supported by project planning based on Bassam Hussein’s book, ”Road to success” [19]. The thesis will mainly involve Phase II of layout planning. Thus, the final outcome is still in an early phase. The choice of layout will be based on investment- and operational costs related to different alternatives.
1.3 Content of thesis
The report is structured as followed:
Chapter 1: Will give an introduction of background and motivation for the thesis.
Chapter 2: A literature study about floating wind turbines. The expected development of floating wind turbines will be presented, describing the floating wind turbine, as a base 6-8MW wind turbine is pre- sented. Information about different types of floating sub structures will be given, and discussion on advantages and disadvantages for the different types. The supply chain for floating wind turbines is presented, together with a case study on Hywind Scotland. Different assembly configurations will lastly be presented.
Chapter 3: Theory that will be used in the method chapter later is given in this chapter. The theory will mainly be based on ”Systematic layout Planning” by Richard Muther and Lee Hales ([32]), but also bring in elements on project planning from literature in ”Road to success - Narratives and insights from real-life projects” by Bassam Hussein ([19]).
Chapter 4: Will give the methodology of the thesis. In this chapter, the theory from chapter 3 will be done in practice. All the activities that need to be done and the relations between them will be mapped out, and finally, a set of layout design will be developed.
Chapter 5: The results and conclusion will be given. The result in this thesis is an overall layout design of an assembly port for floating wind turbines.
Chapter 6: A discussion on the choices that were made early in the design process and evaluation if these were good choices. A discussion on the progress towards the final design will also be presented and eventual changes that could be made to improve the results.
2 Litterature study
In this chapter, background on different aspects of floating wind turbines will be presented. This is in order to get a clearer picture of the expansion of floating wind turbine production. The market segment on wind turbines worldwide is essential in order to justify the need for expansion. It is also beneficial to get an understanding of how large and heavy the different components of a FOWT are. This is to acknowledge the complexity of assembling them, and the importance of the assembly port when large capital costs are needed. In order to see the relations between component suppliers and engineering companies, one has to learn about the supply chain. An example presented is Hywind Scotland to get an overview of how a supply chain can be done.
2.1 The turbine
The turbine itself can be divided into several parts, and the different components are often produced at different world locations. The main components constitute: floating substructure, tower, hub, nacelle, and blades. In this chapter, a short explanation will be presented, supported by a description of how they are connected. Due to its importance for the floating structure, a short explanation on anchor systems for floating wind turbines will be briefly presented.
2.1.1 Typical dimensions for a 6-8 MW floating wind turbine
Sizes of a 6-8 MW floating wind turbine is presented in table 1 and 2. This is the typical size of a floating wind turbine today, for example in Hywind Scotland where the turbine size is for 8 MW.
Part weight of Geometry Possible transportation method
component
Nacelle 300-400 tons ca 15 m long and Either transported in one 6 m high piece, or in several pieces overland Blades 30-40 tons per blade 70-80 meters length(one blade) Transported at sea mostly
width: 6.2-6.5 m if difficult/small roads
Tower ca 400 tons Height: 75-140 m Often transported in 3-4 pieces by ship (whole tower) Diameter: 4-7 m
Hub 50-90 tons 3-6 m diameter Transported in one piece
Table 1: Typical dimensions for a 6-8 MW floating wind turbine [10][23]
Floating Draft Draft Width(d) Displacement installation depth sub-structure (transit) (installed)
Spar 10-80 m 80 m 8 m 13000-15000 tons 120m+
(depending on installation)
Barge 15 28 18 5000-8000 tons 40+
TLP 8-10 m 30 m 42-70m 4000-8000 tons 60m+
Semi-sub 10-12m 20m 50m 6000-8000 tons 40m+
Table 2: Typical dimensions for a floating wind turbine foundation [45][10][23]
Further in this thesis, designing a port layout, these are the main dimensions that will be used, as these are the most standard sizes used today. However, the turbine sizes are expected to grow up to 20 MW in the future. It can be argued that the wisest choice is to follow this trend, and use larger sizes as a base.
However, since the floating wind segment is still immature, and there is a desire to create an assembly port to mass-produce wind turbines, it can be advantageous not to take on too much. Instead of making the larges turbines of the future, use designs known and maintain the control, and reduce the risk of a possible failure. Especially since the investment costs are significant.
2.1.2 Floating substructure
There are several types of floating substructures available in the market. In figure 1, four different types are illustrated: Spar, Barge, Tension leg platform and Semi-submersible. The floating substructures listed use combinations of three different stabilization concepts: mooring line stabilizer, buoyancy stabilized structures and ballast stabilizing. The stability concepts can be directly linked to external ”help” for stability, shown in table 3.
Gravity Water-plane inertia External constraints for stability
Spar Barge Tension leg platform
Semi-submersible
Table 3: Stability for substructures [36]
A lot of skills and knowledge are transferred directly from the oil and gas industry to create these structures. Currently, 50 floating wind designs are under development, adding up to approximately 60%
semi-submersible, 20% spar-buoys and 20% barge. Approximately 80% of all floating substructure de-
The potential is assessed as interesting due to its lightweight and minimum footprint on sea bed.[13]
Figure 1: Substructures [40]
The advantages and disadvantages of the different floating sub structures are discussed in table 4. For the design layout, the semi-submersible platform is chosen. This is because of its relative low draft when installed and is the sub structure that is mainly used today.
Substructure Advantages/
disadvantages
Spar-buoy
The spar-buoy is maintaining its stability by having its centre of gravity bellow the centre of buoyancy
Advantages: Simple design.
Competitive/low installing mooring costs.
Withstands wave movements well.
Disadvantages: Can have a draught up to 70-90 m making it difficult to assembly, transport and install the foundation.
Barge
The hull is made of either concrete or steel.
The structure has a frame, which makes the water plane area stabilise its buoyancy.
The structure is assembled on shore and then towed offshore to its final destination
Advantages: Low draught, makes the structure
fit in shallower waters. (can be beneficial for certain ports).
During transport, the fully equipped platform can float on drafts below 10 m. Lower installing costs
Disadvantages: The wave induced motions
can be more critical than the other solutions. More material usage compared to the others (the frame). The fabrication is more complex compared with the other concepts (especially Spar)
Tension leg platform (TLP)
The TLP is a lighter and smaller substructure.
To provide stability the TLP requires full tension on anchor mooring lines. There are currently no TLP-foundations operating.
Advantages: Less critical for wave motions.
Low mass. Can be assembled onshore/dry dock.
Disadvantages: Unstable until the mooring
lines are hooked up. Anchor has to pull up uptil 10 times the force as the other floating platform types.
Because of the need for tension on mooring lines, the areas for the structure are limited to areas without tidal current and fluctuation.
The costs for installing the mooring is higher.
Semi-submersible
The semi-submersible foundation has a hull consisting of three columns connected to each other. The turbine is either located on one of the three columns or in the middle of them. Buoyancy force is what is keeping the structure stable.
Advantages: Used a lot in the offshore industry.
Structure is stable at both under transit and in operational phase, this means the whole structure can be assembled in harbor and towed to its final destination
Disadvantages: High exposure to waves
and the structure has to be above the water line (parts of the steel has to be right at the water line) A very complex structure which will have a
2.1.3 Tower
The primary function of a tower on a wind turbine is to give access to a desired wind resource by placing the hub and rotor at a favorable height. It also transfers the loads from the top of the turbine down to the foundation. The tower typically has a cylindrical or conical shape and hollow inside. The design of a floating offshore wind turbine is very similar to an onshore wind turbine. However, the marine environment has to be taken into consideration. Preventing corrosion from the saltwater, and wave exiting and hydrodynamic loads change a lot.[38]
2.1.4 Blades
Currently, the blades of a wind turbine are made out of glass fibers or epoxy matrix composites. However, many experiments are taking place using other composites like natural composites, hybrid and nano- engineered composites. The blade’s two sides work as the suction and the pressure face. These are joined together by stiffeners linking the two parts together. The blade constitutes the highest cost component of a turbine, majorly because of the high labor costs. [30]
2.1.5 Nacelle
The nacelle houses the generating components in a wind turbine, including the generator, gearbox, drive train and brake assembly. The nacelle will rotate according to the wind direction, to maximize wind utility. Inside the nacelle, the kinetic energy from the rotating movement is transformed into electricity.
[43][8]
2.1.6 Anchor system
The structure is attached to the sea bottom by use of an anchoring system. The anchor lines are under tension, ensuring the stability of the system. The anchors are embedded by pulling the anchors over the seabed, and as they are dragged along the bottom, the design of anchors makes them penetrate the seabed. The harder it is pulled, the deeper it will penetrate.[48] If there are several turbines in place, several can be attached to the same anchor. This will reduce the number of anchors per unit and thereby reduce cost. The anchor lines are made from steel chains. However, in the future other materials might be used depending on the underwater conditions. Several designs for the anchors are often similar to what is used in the oil and gas platform mooring. The depth range of the turbines to be installed will vary between 60-100 meters. If the depths are shallower than this, there will be technical challenges regarding the stretch in the shorter lines. Floating wind turbines are more competitive as the depths increase.[48]
2.2 Supply chain
In brief, a supply chain may be described as the configuration, coordination, planning, procurement, con- trol, and follow-up of all involved actors and processes involved to create one specified product. The term supply chain management refers to the different methods, theories, and practices used to achieve the opti- mized logistic chain for efficiency and costs. The production milestones may be contract signing, the start of production, launching and start of activities (for example, floating wind turbine), and product delivery.
All types of industrial activity have to manage their supply chain, and procurement of commodities or production facilities often constitute a major part of the cost associated with the production. Tradi- tionally, the yards were specialized and built certain types of ships. They were integrated, meaning that most of the parts were produced and assembled in the same yard. However, today the yards have to broaden their production to cope with the changing markets places. To take part in these markets, some of the production steps are outsourced to other companies or suppliers. Common practice today is out- sourcing most of the production and different levels of outfitting to external companies. The operations in yards focus on systems procurement, integration, and complete the assembly. This is also what we see in offshore wind turbine production. [41]
ported by a timeline and clear descriptions of roles and responsibilities. There are different levels of integration between suppliers and sub-contractors, depending on ownership structures. Work-intensive production lines are often outsourced to low-cost countries, while production lines implying a high level of automation are dealt with by competence-intensive producers, typically located in more industrialized countries. Like most industries, yards are also moving in the direction of automation. The degree of usage of technology and digitization needs to be decided in comparison to human labor. If it is desired to reduce human labor, an automation strategy must be set and integrated with the supply chain strategy. There are different approaches for different levels of product customization vs. standardization. (however, in wind turbine case can be seen as highly standardized).
Figure 3: Simplified sketch of main actors in production of a floating wind turbine 2.2.1 Integrated supply chain
In an integrated supply chain, the chain members are or behaving as they are all under the same com- pany. An integration approach can be designed as different ”levels”. One firm can merge with another firm in the supply chain or share information and work towards an exclusive collaboration with chosen suppliers and customers. This approach enables the different actors to benefit from each other, and the company/constructor has a steady, reliable business. An integrated supply chain will reduce the number of intermediaries and thereby simplify supply chain management. The approach facilitates closer coordi- nation between delivery, warehousing and transportation. If a producer has an integrated supply chain, it can deliver orders faster and adapt quickly to market changes.
2.2.2 Example of supply chain management for floating wind projects set in production:
Hywind Scotland
Commercial floating wind turbines are still at an early phase of development. Several singly turbines have been tested and installed since 2007. However, Hywind Scotland is the first, and for now, only commercialized floating wind farm. A look into Hywind Scotland’s suppliers has been done.
Hywind is a floating offshore wind concept owned by Equinor. The concept consists of 3 floating wind turbine projects: Hywind Demo, Hywind Tampen and Hywind Scotland. Hywind Scotland consists of five floating wind turbines located outside of Scotland, each with a capacity of 6 MW. The farm has been in production since 2017. [20] The concept was developed in 2001, and then the pre-commercial phase started in 2017. The supply chain utilized in the production of Hywind Scotland not integrated, as seen in figure 4.
Figure 4: Supply Hwind Scotland To create the floating wind turbines in the wind
park Hywind Scotland, parts from different suppli- ers were sent to Stord, Norway, for assembly. Sta- toil (now Equinor) itself selected contractors for each element of the project. Before selecting sup- pliers, Statoil ran their supplier database to assess the potential suppliers. An essential selection cri- terion was that the relationship with the suppliers was trustworthy to reduce the risk of failure or miscommunication.
The blades and nacelles where sent from Den- mark. The towers were constructed at Navacel in Bilbao, Spain. The mooring lines that make sure the structure stays in place and the floating sub- structures were brought from Spain (Vicinay the mooring lines and Fene the substructure). Nearly all parts were transported to Norway for assem- bly. The exceptions were the mooring lines and anchors, which were brought directly to Scotland for installation. After the assembly in Norway, the
wind turbines were towed to the same site, 30 km from the coast of Scotland.
Scotland, as a suitable port for assembly. This port is a former fabrication of oil and gas platforms, but there was a lack of storage space, cranes, and simultaneous installation challenges.[28] In the end, Kishorn missed the contract to NorseaGroup’s Stordbase (west coast of Norway) due to lack of infrastructure, and there was no track record.[28]
The floating project developers could choose a site that met the requirements, and maybe as important - choose a port they were familiar with. Further in the project, local suppliers of required equipment could be used. This was an advantage both due to the geographical closeness and a known and trusted supplier. This contributed even further to more production in Norway rather than in Scotland. Another contributor to get supply from several countries in Europe was the market uncertainty within the floating wind industry. The local suppliers could not be guaranteed that there would be several missions after this one, and therefore the local suppliers would not make investments in infrastructure and capability upgrading. [1][35]
2.3 Assembly methods
There are several techniques for assembling the components of a turbine. Looking at the turbine itself, there are a number of ways it can be assembled and mounted to the floating sub structure.
Figure 5: Turbine parts
As seen in figure 5 the turbine consists of 1 nacelle, 1, hub, 3 blades and 1 tower in 2(or several) parts.
Possible ways of assembling these in port are presented in table 5.
6 lifts 5 lifts 3-4 lifts 3-4 lifts 2 lifts 1 lift -Lower tower section
-Upper tower section -nacelle and hub -blade 1 -blade 2 -blade 3
-Assembled tower -nacelle and hub -blade 1 -blade 2 -blade 3
-Assembled tower -nacelle
-hub with blade 1,2
”bunny-ears”
-blade 3
-Assembled tower -nacelle
-hub with blade 1,2,3
”Star assy”
-Lower tower -Upper tower with nacelle, hub and blades attached
-Fully assembled turbine
Table 5: Assembling a turbine [39]
Each of the assembly methods requires different port equipment. For example, the six lift method only requires one heavy-lifting-crane for the nacelle. The 5-lift method might require two heavy lifting cranes, as the assembled tower must be transported after being assembled and lifted from quayside to the floating wind turbine. The same one crane can possibly do this. However, these are cost evaluations that must be done systematically later in the design process.
Further on in this thesis, the ”Star Assy” method has been the base, as this is the same method that was used for Hywind Tampen [11]. Using the same method as Hywind Tampen assembly did, it might be discovered later in the design process of the port, some new solutions or combinations of the Hywind Tampen and this master thesis’ solution. From this, an even better layout design can be made. However, this will be further work and will not be done in this thesis.
3 Theory
In this thesis, theory from ”Systematic Layout Planning” by Richard Muther and Lee Hales, 4th edition [32] has been used as a tool to perform systematic layout planning. The purpose of designing a layout is to make a practical, cost-reducing and safe plant.
For project planning, theory from ”Road to success - Narratives and insights from real-life projects”
by Bassam Hussein has been used [19]. The main objective of project planning is to address when certain activities must happen and the relations. In this way, consequences of delays can be identified. Resources needed in the plant will also be presented, and evaluation can contribute to cost reductions.
3.1 Phases of layout planning
The assignment is limited to only design the general overall port layout. This means phases I, III and IV are omitted. Simple flow patterns and areas linked to the activities are put together and create initial drafts of sizes, contexts, and configurations for each main area. For further work, more detailed plans can be made in phase III.
Phase I: This phase is about determining the location of the area to be laid out Phase II: General overall layout, where a general arrangement is established.
Basic flow patterns, and the areas needed, the relationships between areas are established. A rough layout is made.
Phase III: Detailed layout plans, where each specific piece of machinery is placed.
Phase IV: Installations phase, where approval of the plan and making the physical moves happens.
Table 6: Phases of Systematic Layout Planning [32]
These four phases happen chronologically. However, there will be overlaps. It is assumed that an appropriate location in phase I has been chosen and that all requirements are met. The further into the project, the more details will be decided and locked. After phase II, there is still room to make significant changes. When the physical installation begins, phase IV, every detail down to the centimetre will be planned.
The steps in phase II from Systematic Layout Planning is as followed:
• List activities all happenings within the port has to be identified and is set in a chronological order.
• Make activity relationship diagram or flow diagramwhere various activities, departments, or areas are geographically related to each other but without actual space requirements.
• Decide spaces for activities All the areas, or ”things”, to be included in the layout.
• Make pace relationship diagram will be developed by analyzing the size of components, ma- chinery, and other facilities. However, space must be traded with available space. Space required for each activity is connected, and the diagram can be created.
• Make alternative layoutsSeveral space relationships will be made and is essentially a suggestion for a layout. It will be modified until a good result is made.
• Select overall layout Selection of overall layouts will be chosen from the different suggestion in the previous step.
The design alternatives will be tested for limitations, for example, costs, practicalities, storage, scheduling, safety, and employee preference. These layout suggestions will be named after what their main focus is to create a suggestion for layout design.
3.2 Activities and relations
This thesis will be limited to phase II due to time constraints. This is the phase where most decisions are made, which is relevant for the longest period. All the activities and their relations will be addressed.
3.2.1 List activities
The term activity can be described as ”things” that are included in the port layout. It can be a building, an area, a department, a machine within a smaller layout. It depends on the level of planning of the project at this stage. The rest of the planning and calculations are done from this list of activities, and identifying all of the activities early in the project will save time later in the planning.
3.2.2 Deciding flow of materials
In order to determine the most effective sequence of moving materials or components through the port, the magnitude or, rather, the intensity of the moves must be addressed. An adequate flow is desired. This means that the components move progressively throughout the process, with as few detours as possible.
The flow analysis varies with quantity and number of types. As the product is standardized, the operation process chart or a similar flowchart can be used.
As a material, or in this context, components, are moved through the process in port, six main activities that can happen:
1. Operation: Formed, treatment, assembling, disassembling with other components/materials 2. Transportation
3. Handling (pick-up, set down, re-oriented) 4. Inspection, counting, checked
5. Storage
The different activities has different symbols to represent the activity.
Figure 6: Activities in flow of materials
3.2.3 Relationship chart
A relationship chart shows the relationship between activities. It shows which activities have a relation to others and a rating of importance, and a reasoning code. It is an adequate representation of the different steps and makes it easy to integrate more activities later in the project by adding another row.
There is one separate ”box” for every relationship, and therefore the chart is very detailed in the sense of multiple smaller actions. All the boxes are split horizontally. The upper half shows the importance of relationship, and the lower half shows reasoning for the importance.
3.2.4 Relationship diagram
For deciding the location of the different activities, an activity relationship diagram is convenient to make.
This can be made from a combination of the operation process chart and the relationship chart. This diagram illustrates the flow and importance of closeness between the different activities and gives a visual picture of the data gathered. The relative importance of the closeness of each activity is transferred into a geographic arrangement.
The diagram can be presented using only closeness ratings recording on the relationship chart.
The activities in the different areas are similar as to show the flow of materials (as in figure 6), however in this case, what is happening in the specific area is described.
Figure 7: Activity areas in relationship diagram Conventions for diagramming (page 6-5)
For an even more describing diagram on relationships and a clearer overview, a convention for diagram- ming is useful. Therefore some cedes are made in order to illustrate:
• symbol to illustrate the type of activity
• letter/number for identification of activity
• a specific number of lines to illustrate the importance of closeness (colours can also be used or added)
• Color for the types of activity
3.3 Project planning
To help planning a layout, some schedules showing when the different activities shall happen, and illustrate their relations. There are several helping tools that can be used for this, for example Network diagram, Network analysis and Resource chart.
3.3.1 Network diagram
The chart gives an overview of which tasks are dependent on each other and which tasks can not start before another has ended. In order to illustrate these dependencies, a network diagram can be used. A set of activities: A, B, C and D, can be represented as a box called a node, and the lines that link the nodes together represent the relationships. This network is called Activity On Node (AON). If activity B follows activity A, B is called a successor to A, and A is the predecessor activity of B. [19]
There are four types of dependencies between activities in a network diagram. These states weather next activity dependent on how far the first activity has gotten. To illustrate, activity A is the predecessor, followed by activity B, which is the successor:
• FS: Finish-to-start dependency means activity B can start when activity A is finished
• FF: Finish-to-finishdependency is used when activity B cannot be finished before A is finished
• SS: Start-to-startdependency means activity A cannot start before activity B has started
• FS: Start-to-finishActivity B cannot start until activity A is finished
3.3.2 Network analysis
After the list of activities has been made, an analysis of the AON network will give valuable information on how long time the project needs for completion, what activities affect the completion date, how much
”extra” time is there in the project, and what are the consequences of changing the time constraint for an activity.
To analyse the AON network, information on the activities, and estimate of the duration of each activity, and the dependencies between the activities. A list of parameters will help to make an analysis and present the results:
ES Earliest start for an activity EF Earliest finish for an activity LS Latest start for an activity LF Latest finish for an activity T Duration of activity
Float Extra time avilable for an activity Table 7: Variables for activities
An algorithm is developed called ”the critical path method” (CPM) to calculate these variables. This will, in the end, give the total duration of the project. First, the ES and EF are found for all activities, followed by go through the network to find LF and LS. The float can be found, calculated as the difference between EC and LS, and the critical activities will be the activities with the least float.
To calculate the variables, following equations are used:
EF=ES+T (1)
LS =LF−T (2)
F loat=LF −EF=LS−ES (3)
• ES for the first activity = 0
• ES for a subsequent activity = highest EF of all predecessors
• LF for the last activity = EF
• LF for the preceding activity = smalles LS of all successors
ES EF
Activity
LS LF
Table 8: Variables in an AON network
To find LF for the different activities, one has to work backwards from the last activity. By connecting all activity in a grid with values presented as shown in table 8, the preceding activity value can be found and plotted, giving the critical path. ( hassam, page 139...)
3.3.3 Resource charts
resources. For each activity, some recourse is needed, for example, manpower (or other type(s) of units).
This needs to be addressed, the specific need, to each activity. The resource chart must be drawn up to investigate each unit of time requirements and resolve the resource limitations or constraints/optimize to find the best resource utilisation. The float is also needed to find different ranges of possible solutions,
”feasible solutions”.
For making a better solution with better utilization of resources, some measurements can be done:
• Utilize the float in the network chart by moving the start time of an activity
• Change relationship between activities, however, this might change the total duration
• Transfer resources to a critical activity to a less critical activity to extend the time of a non-critical activity
• Adding more resources to the project (this means increased costs)
3.4 Space determinations
Until now, the activities have been addressed. However, the space determinations have not been men- tioned. Therefore, first, the activities will be addressed to specific areas, and then the activities will be broken down into sub-activities. From this, space for the areas can be calculated from the space estimations of the sub-activities.
3.4.1 Address spaces
As the activity areas have been established, it is time to measure the space needed for each area, its uti- lization (tight or loose), and the required shape of the area, or the overall overview. Usually, determining the required space, a ”take-off” is done on a drawing. What boundaries do the different areas have, and what is needed.
When measuring the space, there are two main strategies:
• Aisles between the activity areas are measured separately
• Aisles are allocated to the specific areas
3.4.2 Equipment needed
Before measuring the space determinations in detail, the machinery needed to perform the tasks must be identified. Each piece of equipment needed for every piece is accounted for by department or activity.
The information will correspond to the activity relationship diagram and the rest of the work.
To maintain an overview of equipment, some helping tools can be used—a scheme for register and archive to record all the equipment and a classification system. Industrial data cards can be a good way of documenting equipment [5].
A classification system for the equipment is also advantageous. This can be a sort of equipment type and then establish a filing system.
3.4.3 Space requirements
There are five main ways to decide the space requirements. They are as followed:
1. Calculation 2. Converting 3. Space standards 4. Roughed-out layout
The order, 1-5, is arranged according to accuracy (number 1 being the most accurate). It is also in order of most frequent use. The different methods will briefly be explained and the method used in this thesis will be explained more detailed.
Calculation method The most straightforward and accurate method of determining the space re- quired is to break each activity into sub-areas that make up the total space.
This one determines how much space each sub-activity needs, how many sub- areas there will be and add them together. Lastly, add extra space.
Converting method In case of an existing yard, one can find what spaces are currently being occu- pied and convert it to what it will contain for the layout. However, this method is not relevant in this case, as there, for now, is no existing yard.
Space standards One can use standards for space requirements for specific machines or space elements. Either find existing ones (however, the standards might differ from country to country, as well as regulations for different purposes). A company can still make its standards, and from this make a suitable working area.
Roughed-out In some cases, layout planning has impractical calculations or converting and no available standards. The on-hand information can be used. For example, templates/models of equipment involved and certain critical activities. One can make rough layouts of certain areas and use them for the space requirements.
This type of planning is suitable for areas with high investments and somewhat permanent systems. The method is suitable for establishing space requirements in phase II, but is expected to have significant changes in phase III.
Ratio trend and projection
The method sets a ratio between space (square meters) and another factor, for example, square meter per unit shipped, labour-hour per year etc. It describes the total/general space requirements and can not be applied to individual areas.
The method is most likely the least accurate method.
Table 9: 5 ways of determining space requirements
In summary, the focus must be on specific requirements for each area, addressing space needed, shapes and configurations. The planner must document and summarize the space amount for each sub-activity, the features and the shape should be indicated as well. The detailed plans do not need to be addressed in phase II. The approximate spaces of each area is sufficient to get an overview and slowly start to combine this with the relationship diagram at this stage.
3.5 Making suggestions on layout designs
The main output of phase II is an general overall layout of a plant. Before the suggested layouts are made, the flow and activities have been diagrammed, as well as spaces required for the different activities mapped. It is time to combine these diagrams in order to create an actual layout.
3.5.1 Flow- and space relationship diagram
An overview of relations and space comparisons is recognised by starting with the flow diagram to see how flows and areas are related. This can either be done with help from a computer or with hand and paper. A paper with cross-section grid lines makes it easier to make correct-scaled areas by giving each square a scale.
To fit the spaces into the diagrams, the spaces can be applied to:
• Flow diagram
• Relationship diagram
• Combination of flow- and relationship diagram
The preferred layout design depends on the relative importance of the supportive devices’ mate- rial flow and relationship. In the space relationship diagram based on the flow of materials, the intensity of flow can be illustrated with arrows representing the flow. The more arrows, the higher intensity of flow.
In the space relationship diagram, based on the relationship diagram, the importance of closeness can be illustrated with lines, just like the relationship diagram. It is desired to have as areas with many lines connecting them as close as possible.
Specific locations that already are decided is beneficial to locate first. This is only if there is no other way to make an innovative and vital solution in case of missing opportunities. The full potential of planning the layout should be done by keeping as many solutions open as possible. Therefore, it is better to work out the space relationship diagram to meet the conditions from the relationship diagram and later adjust to constraints of, for example, existing fixed features in the areas. However, a trade-off must be evaluated on the number of resources that can be spent on keeping ”all solutions open”, or see the constraints early and adapt to these.
When drawing the space relationship diagram, it can be done in two ways:
• Sketching with pencil on routed paper sheets
•
the areas can be converted to a number of squares first, and then start the sketching. If areas have shape requirements, this must be applied. If not, then the most ”reasonable” way to draw will be making the areas square/rectangular shaped. If the sheets are complicated/with many areas and subareas that are to be illustrated, colour-coding can help to make it easier to read.
After making an overview of the relative sizes compared to each other, an even more detailed layout can be developed. The equipment outlining within an area will help to see reasonable solutions, so there will be as few detours as possible for the flows and if the solution is practical. For example, certain in/out entrances and what position they are located in, in the term of flow. However, this will be even more detailed in phase III, where templates for machines is more practical for exact placement.
To improve the block layout design further, a set of templates can be made. A method to do this can be copying each area (drawn at scale like in the space relationship diagram), and cut them out. Once cut out, the areas can be resized with scissor and tape. In this way, a large number of templates can be drawn faster than drawing the layout over and over. In this process, the number of squares is not as important as in the final design but is done to see what combinations that are possible. This is a method to see different possible combinations faster. A record should be made of each possible match, see advantages and disadvantages and iterate the way to a good design, and hopefully, combine the best features of each alternative.
3.5.2 Basic systems for movement of materials
It has been systematized three methods on how the material can move through the plant. The materials can move between three different systems, listed and illustrated:
1. Direct system: materials move between areas using the shortest path. Often used when the intensity of materials is high and distances short
2. Channel system: Materials move in pre-established route. Often used when intensity is low and distances long, especially if the layout is irregular or spread out.
3. Central system: Material moves in pre-established route from origin to a centralized sorting area, moving on to destination. Often used when intensity is low, and distances long, especially if the plant area is squared, and control is important.
Figure 8: Systems describing how movements can be tied together [32]
These systems can also be combined in different configurations. One has to find out what is the best system for the specific design layout case.
3.5.3 Evaluation of layout design
After suggestions on layout designs has been made, an evaluation based on certain criteria must be executed. The criteria will be based on investment- and operational costs. What affects these parameters will be individual for different types of layouts. Examples can be buildings, equipment, man-hours, transport costs etc. An evaluation can be done by comparing the benefit versus cost. [31]
4 Methodology
As presented in previous chapter, layout planning is generally divided in four different phases. However, in this thesis the focus in this limited to phase 2: General overall layout. As the offshore wind industry is evolving and adapted to the specific needs for each installation to be made, there is still no standard way of doing this. Currently, each producer of wind turbines has its individual method, depending on size and sub structure type, and the facilities onshore, such as marshalling harbor and storage areas, distance to shore and country regulations. Based on theory from Systematic Layout Planning, there is a need for more standards to be developed over the years to come, capturing also foreseen up-scaling production.
In this case the construction is being assembled onshore. One important reason is to minimise expen- sive lifting on site. On site, the weather conditions are rougher, the wind causing motions on both the floating sub structure and the assembly vessel. In order to maintain flexibility in position of the harbor, the floating sub structure that is being used in this case is a semi submersible barge. As the draught is not as deep as for example spar buoy, this is much more flexible.
Furthermore, the star assembly method is used: the two tower components are assembled on ground, hub and all 3 blades are assembled on ground, where after the tower is mounted to floating sub structure, followed by the nacelle. Lastly the hub and 3 blades are lifted and mounted. Several factors comprise the background for the method chosen; the weight of a turbine on the tower will be skewed, making the turbine tip and challenging to lift and mount ”directly down”. The process will also have little flexibility in terms of weather windows, and it is therefore desired to reduce number of lifts. This is prevent bottle necks for the heavy-lifting-lifts, which is expensive and takes time to use[11].
4.1 Activities when assembling a floating wind turbine
In Systematic Layout Planning (SLP) the activities in port must be identified at an early stage [32].
Each activity is one step in the process from arrival of components to finished assembled floating wind turbine. The level of details for each step may vary. However, it is necessary to know most of the details in order to design a port, with a sufficient split of different activities in the description. The activities are presented in a chronological order, and activities listed in the process are:
1. Ship(s) docking
2. Transportation of arriving components (tower, nacelle, hub, blades) from ship to quayside 3. Arrival of floating sub structure
4. Transportation of components from quayside to storage area 5. Securing of floating sub structure to quay side
6. Storing of components
7. Transportation of tower from storage area to assembly area 8. Transportation of blades from storage area to assembly area 9. Transportation of hub from storage area to assembly area 10. Assemble tower components
11. Assemble blades to hub
12. Preparation of floating sub structure for turbine components 13. Transportation of assembled tower to quayside
14. Transportation of nacelle to quayside
15. Transportation of assembled hub and blades to quayside 16. Lifting of tower and mounting onto floating sub structure 17. Lifting and mounting of nacelle onto tower on sub structure
18. Lifting and mounting of hub and blades onto nacelle on floating sub structure 19. Finishing of floating wind turbine
At the end of each activity, a dot explains what assumptions are being made as basis for decisions going forward in the process of designing the layout. However, at an early stage it must be expected that most likely, will change come later as more analyses are done. The dots represent the decision that has currently been made, based on the assumptions considered reasonable at the design stage. As more knowledge is revealed, this has to be documented and adjustments may be needed.
4.1.1 Activity 1: Ship docking of components
During the construction of a wind turbine, different components will be brought by ship from various locations globally. Depending on the components transported, the ships will need to dock either as a cargo vessel, with long side along quay, or as a ro-ro vessel with bow or stern to quayside.
• Blades and tower components will be lifted off the vessel using cranes (Lift on/Lift off: Lo-Lo)
• Nacelle and hub will roll on and off the vessel (Ro-Ro)
4.1.2 Activity 2: Transportation of arriving components (tower, blades, nacelle, hub) from ship to quayside
Figure 9: Tower to port [39]
As components are brought to the quay, efficient lifting of the tower component off the vessel is crit- ical. Cranes will carry out the lifting. The cranes may be located on the quayside, or the cranes may be located on the vessel. The tower will be lifted by two cranes, as the tower’s shape is oblong and can be challenging to manoeuvre with only one. The required lifting height will be from the ship side to quay at high tide. The top and bottom of the tower components both constitute assembly-points for the tower, and these points provide usable lift- ing attachments. The tower can also be loaded off the ship by braces around the tower [39].
The nacelle has a compact body and is, therefore, easier to navigate than blades and tower. However, as the nacelle is the heaviest component of the construction, navigation may represent a challenge. In addition, the nacelle has a complex inventory, so due care must be taken when moving the component.
The nacelle may be unloaded to port by cranes from the ship’s deck or rolled off a ro-ro vessel on self- propelled modular trailers, as illustrated in figure 10, the latter is the less costly method [39]. Nacelle must be protected against shock, supported by shock isolates or shock absorbing pallets [47].
Equally, the hub may also be transported from ship to quay, either lifted by crane or rolled off by Self Propelled Modular Trailers. The hub must be regarded as an electrical component, equipped with several monitors. Like the nacelle, careful handling is needed. However, the weight and size are low compared to the other components, so that the handling will be less complicated from that perspective.
Figure 10: Nacelle on SPMT[12]
The process of lifting hub and nacelle to the racks is showed in figure 11. The SPMT will have space to roll underneath the racks, and then the SPMT can lift its platform to lift the component.
Figure 11: SPMT lifting nacelle/hub
Figure 12: Blades arriving in port [46]
The blades are the lightest component of the turbine (stated in table 1). For effi- ciency purpose it is often transported three at a time on racks, still making it one of the lightest components. However, due to its long shape, it is still challenging to handle in port. The blades requires a frame to hold it in place, one at the hub end, and one along the blade span if lifted one at a time, or two-point-contact lifting with cranes if on racks [39].
